U.S. small business manufacturingisgrowing again by inventing new industries and business processes, says PayNet, a small-business analytics and risk-management company.

The PayNet Manufacturing Index, which measures the amount of investment by small manufacturing businesses in property, plant, equipment, tools, and business units, is up 48 percent since 2009, led by the core industrial machinery and equipment sector.

According to PayNet, the index for the industrial machinery & equipment group, which builds gas compressors, carburetors, machine tools, and industrial fans, has fully recovered and grown to 102 points.

"This sector is the biggest example of the resurgence of U.S. manufacturing," says William Phelan, president of PayNet Inc. "The process of re-invention and re-creation is core to business right now, and surviving companies have figured this out."

Instruments producers are growing as a percentage of all manufacturers, as the instruments manufacturing index stands at 123 points. Instruments producers are embedding technology with a growing use of advanced sensors in gauges and monitoring systems. Electricity meters are more accurate today because they use digital sensors and they save energy consumption. They link with the Internet to provide site monitoring and alarms, as well as measure the power quality.

Transportation equipment manufacturing is also enjoying resurgence; these manufacturers are investing 12 percent more now than in 2006, PayNet says. Also, fuel-efficient trucks represent a significant market that has filtered through to the small business manufacturers, and the recovery of car parts, accessories, and demand for aircraft parts is another big driver of investment in this segment, the company says.